Quantitative Molecular Imaging
Imaging is usually performed in order to verify the presence or absence of a specific biomolecule. In typical Western blotting applications, for example, the presence of a protein of interest is confirmed and quantity is determined by a subjective estimate of “blackness” or “thickness” of a band.
Although it may sometimes be sufficient to confirm protein presence and roughly estimate the amount, many analyses of gels and blots greatly benefit from documented information on protein quantity, in either relative or absolute terms.
Quantitative imaging implies a definition of the amount of a specific biomolecule in a sample either in relative terms, for example when comparing expression of a protein in cells in the presence or absence of a growth factor, or in absolute terms where expression is calculated as a given molarity.
Modern light emission-based detection technologies, when used in combination with CCD camera based-imagers or laser scanners, deliver precise quantitative data over a wide linear dynamic range and thereby introduce quantitative analysis to techniques that have previously been regarded as semi-quantitative at best.